Proper wiring of the nervous system requires interplay of intrinsic and extrinsic signals that shape neurite development, architecture and function. Whereas axonal development is relatively well understood, less is known of the forces that shape dendrites, especially the nano-scale filopodia that decorate developing dendritic shafts. What factors influence dendritic filopodia during wiring of brain circuits? Do filopodia contribute to formation of dendritic spines, sites of synaptic information processing and plasticity? We hypothesize that chemical cues in substrate-bound gradients instruct dendrite morphogenesis and maturation via nanometer-scale changes that transform collateral filopodia into spines. We will build upon our recent success in culturing hippocampal neurons from early post-natal rat at very low densities in refined microfluidic environments. Centered in neuroscience, this R21 proposal bridges with materials science to create and exploit complex gradient chemical fields-ones embedding nanometer scale design rules and capable of imprinting the physical environments of neurons in culture with specific immobilized and diffusive factors. These experimental competencies are provided by state-of-the-art microfluidic systems that exploit a variety of physical behaviors to actuate programmed chemo-temporal profiles within the device. Specific aims are to: 1) characterize collateral filopodial behavior in response to 2D surface gradients of bioactive molecules, and 2) build upon these findings to construct 3D gradient environments that encourage filopodial differentiation and enable responses to diffusive stimuli. Models are hippocampal neurons of early post-natal rat and EGFP-actin transgenic mouse. We seek to discover novel insights, solutions and applications that impact mental health, neural repair and restoration of function. The intransigence of brain disorders and damage to treatment is of rising concern as many incurable conditions (schizophrenia, depression, Parkinson's and Alzheimer's disease) have huge economic costs and will increase with the aging of our population. PUBLIC HEALTH RELEVANCE: Nano-scale Processes of Dendrogenesis Proper wiring of the nervous system requires interplay of intrinsic and extrinsic signals that shape neurite development, architecture and function. This proposal seeks to understand the role of nano-scale filopodia in hippocampal dendrogenesis and spine formation by bridging neuroscience with materials science to create and exploit complex gradient chemical fields embedding nanometer-scale design features in nanoliter physical environments. This innovative approach positions us to discover novel insights for normal dendritic spine formation that will offer new strategies, solutions and applications that impact mental health, neural repair and restoration of function, which are of rising concern as many incurable conditions (schizophrenia, depression, Parkinson's and Alzheimer's disease) have huge economic costs and will increase with the aging of our population.